Why do we force the lazy python?

Why do we force the lazy python?

[jgart]

Hi Guixers,

Why do we check if python is a promise and then "force" it?

I'm just trying to understand the thinking for doing that since I didn't
write this code.

```
(let ((python (if (promise? python)
                  (force python)
                  python)))
     ...
```

I understand that force makes a promise evaluate (laziness). That's
about as much as I know.

guix/build-system/python.scm:119

all best,

jgart

Re: Why do we force the lazy python?

[Ricardo Wurmus]

jgart <jgart@dismail.de> writes:

> Why do we check if python is a promise and then "force" it?

See the comment in this definition:

(define package-with-python2
  ;; Note: delay call to 'default-python2' until after the 'arguments' field
  ;; of packages is accessed to avoid a circular dependency when evaluating
  ;; the top-level of (gnu packages python).
  (package-with-explicit-python (delay (default-python2))
                                "python-" "python2-"
                                #:variant-property 'python2-variant))

-- 
Ricardo